The present embodiments relate to a method and an apparatus for representing a blood vessel including a thrombosed section of a blood vessel of a patient.
A thrombosis is a vascular disease in which a blood clot (e.g., thrombus) forms in a blood vessel and partially or completely obstructs the blood vessel. Thrombi may appear in any blood vessel. In ischemic stroke, which is the most common form of stroke, a thrombus obstructs an artery. The thrombus leads to reduced perfusion of the supply area located at the distal end.
To treat vascular diseases (e.g., thrombosis), it is a known procedure to insert a mini-catheter into the patient's vascular system in order to dissolve or remove the thrombus. A current method is “mechanical thrombectomy” using a “stent retriever”. This involves guiding the stent retriever through the thrombus and inserting a mesh (e.g., similar to a stent) along the length of the thrombus. After a short time (e.g., about 5 minutes), the wires of the stent retriever have become entwined with the thrombus, and the stent retriever may be extracted from the vessel together with the thrombus that is caught up therein.
In the procedure described above, the challenge is to grasp hold of the entire thrombus with the stent retriever mesh. If this is unsuccessful and only part of the thrombus is removed, fragments of the thrombus may be deported to other branches of the vascular system distal to the original position of the thrombus. This may lead to considerable negative effects (e.g., to a further obstruction in the distal vascular area). It is therefore important for the physician treating the patient to know the position and the length of the thrombus so that the physician may: a) navigate safely and reliably through the thrombus (without perforating the vessel); and b) push the distal end of the stent retriever far enough forward for the stent retriever to reliably grasp hold of the entire thrombus.
A known method for visualizing the vascular structure is digital subtraction angiography (DSA), in which a contrasted X-ray image (e.g., X-ray image after administration of a contrast agent) is subtracted from a native image (e.g., mask image, image without administration of contrast agent). Thus, the resulting image then contains only the blood vessels marked with contrast agent, with at least extensive blanking out of the background (e.g., soft tissues, bone). If the thrombus is located in an artery, the contrast agent is supplied arterially, for example. Due to the vascular obstruction by the thrombus, however, the contrast agent stops at the proximal end of the thrombus, such that it may not be possible to determine the position and length of the thrombus. The physician consequently lacks information on the vascular course of the artery in the area around the thrombus and also on the overall length of the thrombus.
A partial solution to this problem may be achieved by carrying out 3D scans (e.g., volume scans) involving intravenous administration of contrast agent. If the waiting period between the administration of contrast agent and the acquisition of the 3D scan is sufficiently long and the collateral supply to the obstructed vascular segment is at least adequate, the thrombosed vessel fills up in a retrograde manner (e.g., backwards) and consequently indicates the distal end of the thrombus to the physician. Thus, the positions of the proximal end and the distal end of the thrombus are therefore known to the physician. However, this procedure is comparatively expensive and time-consuming.
Even when all the parameters of this both technically and “practically” complex scan (e.g., contrast agent protocol, timing, collateral blood supply, type of reconstruction) have been successful, the following data is still incomplete or not available: a) Vascular course of the thrombosed vessel; only the proximal and distal ends of the thrombus are known.
Within the thrombus, the physician has to navigate “blind”, however, so that there is a high risk of vascular injury (e.g., of perforation). The following data also is still incompletely or not available: b) Length of the thrombus; depending on the course of the vessel (e.g., straight or curved) between the known fixed points (e.g., proximal and distal end of the thrombus), there are different lengths of thrombus. Since the thrombectomy device to be used (e.g., a stent retriever) may be aligned as much as possible with the length of the thrombus, the image does not make the physician aware of the optimum length of the device to be used. Too short a stent retriever leads to the aforementioned problems. An unnecessarily long stent retriever leads to increased difficulties in navigating through the vascular system and consequently increases the risk of vascular injury.